Ultra-thin single band metamaterial inspired absorber with suppressed higher order modes for terahertz applications

Abstract

An ultra-thin single band metamaterial (MTM) based perfect absorber with suppressed higher order absorption modes is presented in this paper. The unit cell structure is comprised of square shaped resonant patch whose sides are attached to interdigitally coupled fingers providing strong cell to cell electromagnetic coupling, which is found to have a significant impact in reducing the effect of higher order absorption modes. The structure is designed to operate in terahertz (THz) regime with a perfect absorption band centered at 1.61 THz. The absorption behavior is computationally studied and thoroughly analyzed using full wave simulations as well as circuit model approximation. The proposed structure exhibited remarkable characteristics such as polarization insensitivity, high absorption level over wide range of incident angles for both TE and TM polarizations and very weak excited higher order bands for TM polarized wave. In addition to that, it is capable to detect thin layers analyte overlays with sensitivity of 550 GHz/RIU. The absorber is very compact, where the overall thickness is about 1.67% of the wavelength at resonance. Furthermore, it could be viewed as continuous medium since the achieved cell size is around 0.1 times the operating wavelength. The absorber has the potential to be utilized in removing the unwanted peaks in thermal emission and detection as well as in rejecting unwanted modes in resonant structures such as accelerating cavities. It also might be applied to other classes of resonant structures.